LAN gateway designs for multicast communication

The author considers a number of issues regarding gateway design for multicast communication in local area networks. Initially, two designs were considered: (1) explicit identification, in which the source explicitly transmits a message to the gateway, in addition to those already transmitted to the local network; and (2) implicit identification, in which the gateway is promiscuous and receives all multicast messages sent on the local network. It was found that many of the problems associated with explicit identification and implicit identification when used individually could be eliminated by using a hybrid gateway which allowed an explicitly identified parent gateway process to spawn a child gateway which acted as an optimized implicitly identified gateway. The merit of the hybrid gateway is that it allows the source to determine whether the message should be sent to remote networks (an explicitly identified gateway feature), but the actual message transmission is performed by implicitly identifying the gateway